It is previously known, for example, from U.S. Pat. No. 4,219,048, to design the female part with an inner sleeve which, when the male and female parts are connected, is surrounded by an inner wall in the male part at its front end. In this patent the purpose is to obtain, during coupling, a sealing function by means of a sealing member arranged in the inner wall. After a predetermined insertion distance, a lifting surface at the front section of the male part activates the inner sleeve which, by means of the pushing force in the male and female parts, is lifted out from its sealing position to open a media passage which extends in the female part, among other things, via the inside of the inner sleeve.
Couplings of this type must satisfy present day requirements for easily-effected coupling under various coupling conditions. Among other things, there should be a simple and smooth coupling function, even if the chamber of the male part conveying the media or containing the media is under excess pressure during the coupling movement of the coupling parts. Thus, for example, the coupling should take place, without any risk of media leakage during the coupling, when the media pressure in the male part assumes values of up to 40 MPa (400 bar).
This requirement should not mean that the coupling parts have to be of a complicated technical construction, the flow area in the coupling parts is reduced, and the like. A further requirement is that it must be possible for coupling and decoupling to be carried out with a very high degree of freedom from leakage.